A recent Supreme Court order for India to proceed with a massive project to divert water from flood-prone areas to drought-ridden ones is raising concern in and outside India for environmental and security reasons.

Environmentalists have appealed to the court to rethink the decision, which would see 80 dams as well as kilometres of canals built on 37 rivers.

Meanwhile, Bangladesh, Nepal and Bhutan have expressed concern about the project as all three countries share river systems with India. India would have to work out international agreements with all three countries to go ahead with its plans.

The project "is bound to have major environmental and ecological consequences, not to speak of immense hardship to people who will be displaced as a result," said a group of Indian environmentalists and lawyers in an open letter. "The project not only holds the potential of generating new inter-state conflicts but also has serious international dimensions that need to be considered."

With a population of 1.2 billion people and growing, water is already scarce in many parts of the country, with states fighting over their share of river water.

The National Water Development Agency, the agency responsible for carrying out the project, said that by 2050, India's population will reach 1.8 billion. To meet expected demand for food grains, the agency estimates that it will be necessary to irrigate 160 million ha for all crops, up from the present 140 million ha.

The water plan, first suggested by the previous Bharatiya Janata Party government in 2002, is expected to cost upwards of US$120 billion (S$151 billion). It has two major parts: a peninsula plan of 16 links to create a southern water grid, and a Himalayan plan of 14 links through dams and canals.

Though put on the backburner by the current Congress-led government, the Supreme Court revived the scheme on Feb27, appointing a committee and asking it to move forward on linking the rivers. "This is a matter of national benefit and progress... saving the people living in drought-prone zones from hunger and people living in flood-prone areas from the destruction caused by floods," the Supreme Court order said.

Neighbouring countries Nepal, Bhutan and Bangladesh say the Indian government has yet to approach them about the vast project.

"This (interlinking) is completely unimplementable. In India, water is the state's jurisdiction. All links will require water transfer from one state to another. In 10 years (since the idea was proposed), only Tamil Nadu, Gujarat and Rajasthan (which are facing water problems) have said they support it," said Mr Himanshu Thakkar of the South Asia Network on Dams, Rivers and People, which is planning to file an appeal on the court order.

Nepal, where anti-India sentiment is already strong, is worried that India may want to build dams in its rivers which flow down into India.

"It is obvious you can't do this without storage dams in Bhutan and Nepal... You can't plan on resource development in someone else's territory," said Nepal's former water resources minister Dipak Gyawali, director of the Nepal Water Conservation Foundation.

Bangladesh is even more worried, considering that its rivers flow in from India.

'This has been designed to divert water from two main lifelines of Bangladesh namely the Brahmaputra and the Ganges,' said Dr Abdul Matin, a Bangladeshi water resources expert.

Background story: Why its neighbours are unhappy

Bangladesh claims that the flow of the Brahmaputra and the Ganges - two of Asia's major rivers - will be redirected towards southern and western parts of India, depriving Bangladesh, a downstream country, of water.

Nepal and Bhutan are concerned that India's plan includes building dams and canals on their territories. The proposed links include one between Kosi and Mechi in Nepal, which will be joined to Ghaghra and Yamuna in India.